textproduct: Quad Cities

KEY MESSAGES

- High pressure overhead will result in a beautiful start to the work week, with mostly clear skies and mild temperatures.

- Another active weather pattern will set up mid-late week, bringing the potential for rounds of showers and storms with a threat for heavy rainfall.

- Temperatures will remain near to slightly above seasonal norms through the next week.

SHORT TERM /THROUGH TUESDAY/

Issued at 215 PM CDT Mon Sep 28 2026

Beautiful weather for late September will continue with high pressure centered over the Great Lakes and Ohio Valley. Locally, for eastern Iowa and northwest Illinois we can expect mild temperatures and dry conditions. Mainly clear skies this evening/tonight will give way to increasing high clouds through the day on Tuesday. Highs will once again reach into the 70s, with even some upper 70s south of Highway 30 as steady southerly winds advect a warmer air mass into the region.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 215 PM CDT Mon Sep 28 2026

Trough over the eastern CONUS continues to break down through Tuesday/Wednesday, with the ridge that has been locked in place overhead tracking easterly. Upper level flow will then increase out of the southwest as a deep trof digs into the Desert Southwest. A strong fetch of moisture in connection with the Eastern Pacific will set up, directing an unseasonably moist airmass into the central CONUS. This increase in moisture is aided by tropical systems that will get caught in the flow from the Eastern Pacific, serving as a moisture conveyor into the region, with plenty of forcing to favor precipitation chances. Not only will this help supply moisture to the region, but llvl southerly/southwesterly flow will usher Gulf moisture in as well. Thus, an anomalously moist airmass will be in place through mid week, with PWATS between 1.50-2.00" or higher moving in. As such, the WPC has highlighted our area in a Slight Risk, level 2 of 4, for Excessive Rainfall and Flash Flooding for Wednesday and Thursday. The wave digging into the Desert Southwest will slowly traverse over the Rockies, guiding bouts of energy towards the Upper Mississippi River Valley, with a baroclinic zone setting up nearby. This baroclinic zone will serve as a focus for the potential for rounds of showers/storms, with heavy rainfall possible.

Latest model trends have the heaviest axis of QPF across portions of central into eastern Iowa, where some areas could receive over 3" of rainfall from late Tuesday night through Thursday night. However, the exact north/south placement is uncertain. The EC ensemble mean continues to be the southern most solution (and wettest) with the highest rainfall amounts along the I-80 to Highway 30 corridors. Other ensemble models (GEFS/AIGEFS/EC AIFS/CMC) are shifted more to the northwest, but still clip our northwest counties with some of the higher rainfall amounts of 2"+. Given this uncertainty, and since the heavy rain will come in several separate waves Wednesday - Thursday, will hold off on a Flood Watch for now.

The timing has also trended later over recent forecast runs. We were initially looking at the potential first round of showers/storms moving in Tuesday night, but we are now looking at potential onset closer to the early Wednesday AM timeframe. The more widespread rainfall chances will hold off until Wednesday PM and into Thursday (60-90% chances). Through this ~2 day stretch, WPC has a widespread 1.75" to 2.5"+ across the outlook area, with the highest amounts favored west of the Mississippi River. Certainly, localized higher totals of 3"+ are possible. The latest NBM 48-hr QPF probabilities for 2"+ are fairly high between 50-80% (southeast to northwest). We will continue to monitor trends in the forecast, especially as more hi-res guidance comes in.

Late this week and into the weekend, zonal to northwest flow will set up over the region. We might see some weak waves work through the flow, but much uncertainty remains on moisture availability. Guidance has trended drier through the weekend than in previous runs, with chances between 15-30% at this time.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1255 PM CDT Mon Sep 28 2026

High pressure in control over the Mid to Upper Mississippi Valley region will result in quiet weather with prevailing VFR and light winds through the period.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.